Today it is of outmost importance to present correct flight safety critical primary data, such as altitude or roll angle, to an operator of a platform, e.g. a pilot of an aircraft. In aircrafts there are often at least two independent systems provided for generating flight safety critical primary data. Data generated by the two independent systems have to be checked so as to detect any malfunction of sensors of respective system results in false or deviating flight safety critical primary data.
Manual cross-monitoring of flight critical primary data performed by the operator of the platform involves high work load. Also, a stressed or tired operator may more often make incorrect judgements. In airplanes, for example, flight safety critical primary data to be cross-monitored are presented on different display surfaces in cockpit, occupying unnecessary presentation surface area.
Another way of controlling important data generated by separate independent sources is voting. The procedure of automatic voting relates to a system of triple redundant sources meaning that three separate independent sources are used, each generating unique data to be compared. According to one known procedure, the data among the three, which deviates the most, is voted down. This system is bulky, heavy and costly.
U.S. Pat. No. 4,622,667 depicts an automatic flight control system that is fail operational with respect to a generic fault. The automatic flight control system utilizes at least two independent flight control subsystems, each comprising a pair of channels. One channel in each subsystem includes a first digital data processor and the other channel includes a second digital data processor with an active third processor. The two channels in each subsystems are cross-channel monitored to detect disagreements between the outputs of the first and second processors and the outputs of the first and third processors. This system also suffers from the disadvantage of being bulky and costly.
It therefore exist a need to provide means arranged to facilitate the process of cross-monitoring of primary flight parameter data within a platform, such as an airplane.